<!DOCTYPE html>
<html>
  <head>
    <style>
      .custom_scrollbar::-webkit-scrollbar {
        width: 12px;
      }

      .custom_scrollbar::-webkit-scrollbar-track {
        -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3);
        border-radius: 10px;
      }

      .custom_scrollbar::-webkit-scrollbar-thumb {
        border-radius: 10px;
        -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.5);
      }

      #container {
        width: 220px;
        height: 200px;
        overflow-y: scroll;
      }

      #content {
        width: 200px;
        height: 1000px;
        background: silver;
        margin: 0px;
      }
    </style>
  </head>
  <body>
    <div class="custom_scrollbar" id="container">
      <div id="content">
        The custom scrollbar should scroll on main thread.
      </div>
    </div>
  </body>
</html>
